Rename the Config File
This step involves using Windows Explorer to navigate to a directory and change a filename. If you do not feel comfortable doing so, please contact your technical support.
Start by browsing to the following location using Windows Explorer:
C:\Program Files (x86)\Common Files\Microsoft Shared\VSTO\10.0
This location may not exist on your computer. Instead, try the following location in the regular Program Files directory:
C:\Program Files\Common Files\Microsoft Shared\VSTO\10.0
In this folder will be a file named VSTOInstaller.exe.Config. Rename this file to VSTOInstaller.exe.Config.old(adding the ".old" extension), and then retry the installation of vstor_redist.exe.
Running installation as Administrator
In certain cases, vstor_redist.exe needs to be run explicitly as an Administrator on your local machine. Right click on the vstor_redist.exe installation file and choose "Run as Administrator" rather than just double-clicking.